While filter presses are well known in the art, a major problem has persisted in that it has not been possible to determine, during the course of operation of the press, whether the operating conditions were satisfactory for the production of a desired cake within the filter and the preferred duration of the operating cycle. Thus, for example, if the liquid-solids composition or other operating conditions be incorrectly assessed or should change during the filtration process, the termination of a filtration cycle based on a normal cycle or a normal terminal filtrate flow may result in the production of unacceptably wet filter cake with the frequently attendant time-consuming task of washing the filter; or, termination of a filtration cycle based on a normal fitration time, or a normal terminal filtrate flow may result in plugging of the core or feedhole of the filter, which can result, among other things, in catastrophic failure of filter plates.
Historic methods of monitoring the progress of a filtration cycle comprise the discrete observation of pressure, elapsed time and filtrate flow. Unfortunately, these are useful only to the point that conditions remain constant from one filtration cycle to another. Discrete observations are totally misleading and useless as a basis for making process decisions where changes occur, for example, changes in concentration, permeability of the cake being formed or changes in response to the feed of conditioning chemicals.
One object of this invention therefore resides in the provision of filtration method and apparatus for the operation of a filter press wherein the problems referred to above have been overcome through the utilization of a novel and improved control system wherein operating conditions are continuously monitored to insure the production of a desired quality of cake and the termination time for the filtration cycle.
A still further object of the invention resides in the provision of a novel and improved method and apparatus for the operation of a filter press wherein a pilot filter press under control of an improved system for initially insuring attainment of a preferred quality of a cake produced in the filter and determining the duration of the operating cycle and thereafter transferring control to the main filter press thus insuring proper operation of the main filter press throughout the entire duration of the filtration cycle.
Still another object of the invention resides in the provision of a novel and improved method and apparatus for controlling the operation of a filter press.